1. Field of the Invention
The present invention relates to a lens barrel and an imaging apparatus.
2. Description of the Related Art
Recently, an imaging apparatus such as a digital camera and the like which utilizes a solid-state imaging device has been widely used.
In accordance with the spread of an imaging apparatus which utilizes a solid-state imaging device, further improvement of image quality has been desired. In particular, for a digital still camera etc. which utilizes a solid-state imaging device with a large number of pixels, a lens for imaging and especially a zoom lens which has superior imaging performance compliant for the solid-state imaging device with a large number of pixels has been desired.
Further, since there is a strong demand for the camera to be small and slim, a small and slim zoom lens which has high performance and a lens barrel which includes such a zoom lens have been desired. Further, since higher zooming power of an imaging lens is strongly preferred in recent years, the zoom lens which zooming power is over threefold and the lens barrel therewith have been desired even for a compact digital camera.
Generally, a positive-lead type zoom lens which includes a lens group at the most object side having positive refractive power has an advantage in enlarging the zooming power. Therefore, this type of zoom lens is widely used as being suitable for a high power zoom lens exceeding threefold magnification.
In particular, a four-group zoom lens including four lens groups which have positive, negative, positive and positive refractive powers in order from the object side is familiar as a compact zoom lens of the positive-lead type (see Japanese Patent Application Laid-Open No. 2004-212616 and Japanese Patent Application Laid-Open No. 2006-23529).
For a retractable type zoom lens which storage is improved by retracting the lens when the camera is not used (when not shooting), among the four-group zoom lenses, the third lens group which has positive refractive power and moves toward the object as a main variator when zooming is widely used.
This is because the four-group zoom lens of this type is suitable in view of sensitivity against decentering of the lens barrel structure and each lens group. Specifically, the type has an advantage in suppressing the effect of decentering to the quality of the photographic image.
In the case of the above four-group zoom type with the arrangement of positive, negative, positive and positive refractive powers in order from the object side and in which the third lens group functions as a main variator, the sensitivity against the decentering of each lens arranged in the third lens group which performs zooming becomes large. In other words, the effect of the decentering of each lens to the quality of the photographic image becomes large. Therefore, when arranging the lens into a lens frame during manufacturing, it may be necessary to perform attachment while adjusting the position with equipment such as an alignment device and the like (see Japanese Patent Application Laid-Open No. 2007-93934).
Further, the second lens group which functions as a supplemental variator when zooming performs the operation to significantly refract the light beam projecting through the first lens group. Accordingly, since the sensitivity against the decentering of each lens which is arranged in the group easily becomes large as in the case of the third lens group, it may be necessary to perform attachment while adjusting the position with equipment such as an alignment device and the like.